Shelf



FIG. 1 is a front perspective view of a shelf showing my new design. _

FIG. 2 is a top plan view thereof. _

FIG. 3 is a front elevational view thereof, the rear view being a mirror image thereof; and _

FIG. 4 is an end elevational view thereof, the opposite end view being a mirror image thereof. _ 

The ornamental design for a shelf, as shown and described. 